Image persistence
From Wikipedia, the free encyclopedia
Image Persistence is the term used for the LCD and plasma display equivalent of screen burn. Unlike screen burn, however, the effects are most often only temporary. It should be noted however, that plasma displays can also suffer from burn-in (see the plasma display article for more information).
[edit] Cause
Liquid crystals have a natural relaxed state. When a voltage is applied they rearrange themselves to block certain light waves. If left with the same voltage for an extended period of time (e.g. displaying a mouse cursor or the Microsoft Windows Taskbar in one place), the liquid crystals can develop a tendency to stay in one position. This ever so slight tendency to stay arranged in one position can throw the requested color off by a slight degree, which causes the image to look like the traditional "burn-in" on phosphor based displays.
The actual cause for this tendency is unclear. It might be due to accumulation of ionic impurities inside the LCD [1], or electric charge building up near the electrodes [2], or parasitic capacitance [3], or "a DC voltage component that occurs unavoidably in some display pixels owing to anisotropy in the dielectric constant of the liquid crystal" [4].
[edit] Prevention/Treatment
This is easily preventable and can be reversed by allowing the liquid crystals to return to their relaxed state. In other words, turning off an LCD display for as little as 15 minutes a day will relax the crystals and help prevent image retention. For PC monitors, it is also ideal to rotate desktops, and hide away elements on the screen which normally would be displayed perpetually (like the taskbar in Microsoft Windows or the Dock in Mac OS X). The usage of a screensaver that has a constantly changing image can help as well.
The fastest remedy for image persistence is to leave the display off for an extended period of time. This time can range anywhere from hours to days. Another useful approach to removing LCD image persistence is to first create a solid white image and display the image as a screensaver covering the entire display area for an extended period of time.[5]
